Pollution is generallyy defined as the release of harmful environmental contaminants. Pollution can take two major forms: local pollution and global pollution. In the past, only local pollution was thought to be a problem. For example, coal burning produces smoke and in sufficient concentrations can be a health hazard. One slogan, taught in schools was "The solution to pollution is dilution". In recent decades, awareness has been rising that some forms of pollution pose a global problem.

Traditionally, serious pollution sources include chemical plants, oil refineries, nuclear waste dumps, regular garbage dumps (many toxic substances are illegally dumped there), incinerators, PVC factories, car factories, plastics factories and corporate animal farms creating huge amounts of animal waste.
Lead is still the single most important chemical toxin for children and is probably the best known example of a neurotoxin to which children are particularly vulnerable. Their special vulnerability to lead is related to their exposure (hand–mouth activity, ingestion of paint chips),the fact that upon exposure children absorb four times more lead than adults, and their susceptibility at a critical period of brain development.
Children may be exposed to lead in leaded petrol from car emissions, water contaminated by lead pipes, old paint, emissions from factories, contaminated soil and food contaminated by environmental sources (including improperly glazed ceramic ware for cooking and food storage).
Lead particles can move with water, soil, dust and wind.

The neurotoxic effects of lead depend on the exposure level and the stage of nervous system development at the time of exposure. Studies have documented that developmental exposure to lead can adversely affects several specific brain functions, resulting in particular in learning disabilities, attention deficit, poor motor coordination, and inadequate language development. Do a thorough check of your home and always watch what your children are putting in their mouths.